Stabilizers for rubber and synthetic polymers



Patented Aug. 25, 1953 STABILIZERS F SYNTHETIC William F. Arey, Jr.,

. merit Company, a

R RUBBER AND POLYMERS and Robert E. Wood, Baton Rouge, La., assignors to Standard Oil Developcorporatlon of Delaware No Drawing. Application October Serial No. 122,136

13 Claims. (0!. 26045.55)

This invention relates to elastomers subject to deterioration in the presence of oxygen, and it relates more particularly to elastomers containing addition agents suitable for retarding their l deterioration.

In accordance with the present invention, a new class of organic derivatives is described which are particularly useful as stabilizing agents for elastomers.

The new class of antioxidant compounds are condensation products of polyhydric phenols with dioleflns. The condensation is carried out in such a manner that the product contains up to two aromatic rings.

Suitable polyhydric phenols include resorcinol, catechol, hydroquinone, pyrogallol, phloroglucinol, etc. Phenol, itself, may also be used, but the product obtained is inferior to other known antioxidants for rubber. This may be improved by condensing the diolefin with alkylated phenol or alkylating the product obtained. However, in this case, the product is no better than commercially available antioxidants.

Suitable diolefins include butadiene, isoprene, piperylene, dimethyl butadiene, myrcene, dimethallyl and the like. The condensation is carried out under pressure at a temperature above 100 F. in the presence of a hydrate of a Friedel-Crafts type catalyst, suchas FeCla.6HzO, AlCl3.6H2O, AlBra,6HzO, Slick-61120,. etc., until reaction is substantially complete. The diolefin should be in excess of a 1/1 mol ratio of diolefin to phenol. j

Generally, the additives of the present invention are most advantageously blended with the elastomer base stocks in concentration between 0.1 and 2% by weight of the elastomer, although larger amounts may be used for some purposes. The exact amount of addition agent required for maximum improvement depends to a certain extent on the particular products used, and the nature of the elastomer base stock.

Any of the common elastomers (as defined by Fisher in his article of the August 1939 issue of Industrial and Engineering Chemistry, on page 941, under the heading, Nomenclature of synthetic rubber) (see also Hackhs Chemical Dictionary, Third Edition, page 295) are suitable as raw materials for the present invention. The preferred elastomer is thelow temperature interpolymer of isobutylene with a multiolefin having from 4 to 14 carbon atoms per molecule, such as butadiene, isoprene, dimethyl butadiene, myr-.

cene, dimethallyl, or the like. This copolymer is prepared by cooling the olefinic material to a temperature within the range between 50 C. and -103 C.; the mixture being made up with a major proportion of isobutylene and a minor proportion of the diolefin; then treating the cold mixture with a solution of a Eriedel-Crafts catalyst in solution in a low-freezing, non-coma plex-forming solvent, such as a solution of alui on The Friedel-Crafts synthesis,

between about: 20,000 and 150,000;

b r r z minum chloride in a compound such as ethyl or methyl chloride or ethylene dichloride or chloroform, or the like, as

shown in United States Patents Nos. 2,356,127

and 2,356,128.,

The reaction proceeds promptly to yield the desired copolymer. It may be noted that in this reaction the preferred isoolefin is isobutylene, but that a wide choice of multiolefins is possible as above pointed ou i l 4 For the catalyst, any of the Friedel-Crafts catalysts disclosed by N. O. Calloway in his article printed in the published for the Baltimore, in 1935,

issue of Chemical Reviews." American Chemical Society at in volume XVII, No. 3, the article beginning on page 1327, the list being particularly well shown on page 375, may be used. Thesolvent to be low-freezing must have a freezing point below 0 C.; to be non-complex forming, there shall the solvent a compound between the solvent and All of the aliphatic halo-substituted compounds having freezing points below 0 C. are usable as catalyst solvents without regard of the number of halo-substituents or the particular halogen used, and for the Similarly, carbon disulfide and its analogs and homologs are also usable.

catalyst solvents, since they also are low-freezing and non-complex-forming. In addition to the active metal halides disclosed by Galloway,

including such substances as aluminum chiorobromide which has the potency of aluminum chloride and is soluble in hydrocarbons. Similarly, such compound as aluminum or titanium chloro ethoxide are also usable as catalysts in thisreaction. 1

The resulting polymer is a solid having a Staudinger molecular weight number within the range a minimum about 20,000 being necessary (according to the WIJS 50, the preferred range tion to yield a high-grade elastomer suitable for halo-substituted aliphatic 0 many of the uses to which rubber has previously -been put.)

Alternatively, the emulsion interpolymers of butadiene with styrene or acrylonitrile; or of isoprene, either alone or with styrene or acrylonitrile; or dimethyl butadiene, alone or with styrene A number of examples of the preparation of the new compounds of the present invention will be described in detail and data showingthe effect of these additives in elastomer base stocks will also be given. It should be understood that these examples are given for illustrative purposes only and are not to be construed as limiting the scope of the invention in any way.

Example I The following charge was placed in a pressure bottle:

110 grams resorcinol 108 grams butadiene 3 grams FeCbfiI-IzO The bottle was then attached to a rotating wheel in a water bath. 'The reaction mixture was heated to a temperature of 150 F. for 89 hours, at a pressure corresponding to the vapor pressure of butadiene at this temperature. At the end of this time, the bottle and contents wereallowed to cool and the reaction mixture was transferred to a beaker. Excess butadiene was removed by heating on a steam bath. Weight of crude product was 155 grams. The reaction product was washed three times by adding 500 cc. water and heating. on a steam bath while stirring the mixture and then decanting the water. The material was dissolved in isopropyl alcohol, filtered and then the solvent was removed by heating on a steam bath overnight.

The product thus obtained was a dark red (18 on the Gardner scale), viscous (Gardner viscosity of 2-10) liquid and amounted to 150 grams. It was very slightly soluble in sodium hydroxide solution. freezing point depression in benzene was 208. This value and stoichiometric considerations indicate the product to contain two resorcinol and between 1 and 2 butadiene residues.

Charge: Example II 110 grams resorcinol 300 grams butadiene ner Z-lO.

Molecular weight as determined by- Procedure same as in Example'I except heating at 150 F. wasfor 64 hours. Yield of purified product was 150 grams.

Example III Charge same as in Example 1. Procedure same as in Example I except heating was for 5 hours. Yield of purified product was 120 grams; color: Gardner 18; viscosity: slightly greater than Gard- Example IV Charge:

110 grams catechol 108 grams butadiene 3 grams FeClsfiHzO Procedure as in Example II, gave 150 grams of black, rather viscous liquid that was exceedingly staining.

. Example V 20 Charge gramsresorcinol 25 grams plant isoprene (96%) 1 gram FeClsfiHzO Procedure same as in Example I except heating 25 at 150 F. was for '72 hours, and a viscous purple product was obtained, which was dissolved in 500 cc. of isopropanol, evaporated to dryness and .washed twice with 500 cc. of hot water, and evaporated again to dryness, whereupon 50 grams of product were obtained.

Example VI The condensation product obtained in Example I was dissolved in a small amount of isopropyl alcohol and the resulting solution emulsified in soap solution. This emulsion was then added to an uncoagulated latex obtained by the emulsion copolymerization of butadiene and acrylonitrile, the latex was coagulated by salt solution 40 and dried at 165 F. for a period of 18 to 20 hours.

Parts by weight Polymer 100 Zinc oxide 5 Stearic acid l Benzothiazyl disulfide 1 5 Medium process channel black The compounded product was then cured for 45 4-methyl phenol and phenylbeta-naphthylamine,

both of which are oxidation inhibitors known to the art.

3 grams FeClafiI-IzO TABLE I 'Copolymer Stabilizer Drying Conditions Cure 2Minutes geightk Mooney; 32E255, Sample Type Type gaf Z%P" fi g? Viscosity Tensile ggy Elong.

Polymer 0 A 1.0 165 is s2 1 Percent acrylonitrile in copolymer. 1 Uncured gum.

a,eso,2os 5 6 Example VII viscosity recorded after and 10 minutes of hot The reaction product of Example I was added mmmg' The following results were obtained:

on a mill to an unstabilized copolymer of 97% isobutylene and 3% lsoprene. After mixing the 5 5mm, liaxi iza ne polymer was milled at 320 F. and the Mooney viscosity recorded after 15, 90, and 180 minutes wt Per of hot milling. The following results were ob- Type c lm tained:

TABLE II 10 o 11 a1 ttfiittiafimssax i Z1 Sabina ggggsgqsggw Example X 0 15 v 00 1s0 15 The reaction product of Example I was added Type 1 3 1 111 3: Minutes Minut mums in a concentration of 0.25 weight percent on a mill to an unstabilized rubbery polymer of isop 0.3 76 76 1e 76 butylene having a molecular weight of 116,800. 2: 3 3g 3g 32 g; After mixing the polymer was milled at soc-350 F. and observations made on the molecular weight breakdown after the indicated time with A. Stabilizer of Exam lo I.

p the following results:

B". Phenylbetanaphthylamine.

The following results show that the additive Stabilizer causes no serious interference with the curing rate of the isobutylene-isoprene copolymer: A B

TABLE 111 a li t? W -aim 53% if? 8 er mlnu es 5, 80 Stabilizer Modulus afterfiOmiuutes' 86,200 90,260 cure, El after 75 m nutes m ll ng--. 40, 600 Mm T 9 after 90 minutes milling-.. 81, 600 Wt. Per- 0 F. 8116 83MB alter 120 m nutes; m lling 75, 900 Type ggilst gg 300% 400% after 135 minutes milllng 79,000

A-resorcinol-butadiene product of Exam lo I.' A 0 2 2g 5g 1 i 38 B2 ,6-di-tertiary-butyl-i methylphenol.

80 2: 1,070 1, w) 660 From the above data it is evident that with 0.25 20 3,000 480 710 820 I O M 2,950 740 L110 750 weight percent concentration, 33% breakdown 7 1,030 1,560 630 was obtained only after 120 minutes using the stabilizer of the present invention. while breakdown was obtained with 2,6-di-tertiarybutyl-4-methyl phenol in75 minutes and in 13 P 1 53326 minutes when no stabilizer was used. Stearic acld Sulfur Example XI Tetramethyl-thiuramdisulflde (Tuads Mercaptobenzothiazole (Captax)...

Easy Processing Channel Black A-1eaction product of Example I. O-phenylbetanaphthylamine.

3 2 1 13 4 Samples of the 'copolymers of Examples VI and VII containing the addition agent of Example I were compounded with clay and cured to give white vulcanizates. These samples were Example VIII placed on a metal surface covered with. two coats The reaction product of E p} e v was added 50 of white enamel and exposed to the weather for 2 months. The following results show that as a sodium oleate water emulsion in isopropanol solution to an uncoagulated latex obtained by the g g gg product is low'staimng t emulsion copolymerization of 65% butadiene and h TABLE Iv 35% acrylonitrile. The latex was then coagulated with brine and acetic acid. The unvulcanized polymer was subjected to a temperature Adam 0! 170 F. for 38 hours in a forced-draft drier. Polymer The following data were obtained in comparison Type g- 5:5 Color ggalgubber Enamel Under- After 2% Months Exposure with 2,6 -di-tertiary-butyl-4-methyl phenol: Polymer math Slab l. 0 Dark Purple- Stained Purple- Mooney, Brown. Brown. 2Min.at 1.0 Slight Yellow Slight Yellow 212 F. s Do. 13 Polymer without stabilizer 31 Polymer with 2,6-ditertiary-butyl-4- g g gf g methyl phenoln 6 Do A No Stain Polymer with stabilizer of Example V-.-" 94 91-9 Example IX The reaction product of Example V was added on a mill to an unstabilized copolymer, Example I butylene and 15% isoprene. After mixing, the Instead oi. polyhydric phenols, phenol itself or polymer was milled at 270 and the Mooney 75 its alkylation products such as mono alkyl or dialkyl phenol may be condensed with butadiene.

The nature of the present invention having thus been described, what is claimed as new and useful and desired to be secured by Letters Patcut is:

1. A high molecular weight elastomeric polymerization product of a feed containing at least a major proportion of aliphatic hydrocarbon compounds selected from the group consisting of mono-olefins and multi-olefins having from 4 to 14 carbon atoms per molecule and which is normally subject to deterioration in the presence of oxygen, which contains in admixture therewith a small quantity, sufficient to substantially reduce such deterioration, of the condensation product prepared by reacting a diolefin and a polyhydric phenol in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

2. A high molecular weight elastomeric polymerization product of a feed containing at least a major proportion of aliphatic hydrocarbon compounds selected from the group consisting of mono-olefins and multi-olefins having from 4 to 14 carbon atoms per molecule and which is normally subject to deterioration in the presence of oxygen, which contains in admixture therewith a small quantity, suflicient to substantially reduce such deterioration, of the condensation product prepared by reacting resorcinol and butadiene in the presence of a. hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

3. A high molecular weight elastomeric polymerization product of a feed containing at least a major proportion of aliphatic hydrocarbon. compounds selected from the group consisting of mono-olefins and multi-oleflns having from 4 to" 14 carbon atoms per molecule and which is normally subject to deterioration in the presence of oxygen, which contains in admixture therewith a small quantity, suflicient to substantially reduce such deterioration, of the condensation product prepared by reacting catechol and butadiene in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei. V

4. A composition of matter comprising a low temperature rubber-like copolymer of a major proportion of isobutylene with a minor proportion of a multiolefin having from 4 to 14 carbon atoms per molecule together with 0.1 to 2% by weight of the copolymer of the condensation product prepared by reacting a diolefin and a polyhydric phenol in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

5. A composition of matter comprising a low temperature rubber-like copolymer of a major proportion of isobutylene with a minor propor-' tion of a multiolefin having from 4 to 14 carbon atoms per molecule together with the condensation product prepared by reacting resorcinol and butadiene in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

6. A composition of matter comprising a low temperature rubber-like copolymer of a major proportion of isobutylene with a minor proportion of a multiolefin having from 4 to 14 carbon atoms per molecule together with the condensation product prepared by reacting catechol and butadiene in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

7. A composition of matter comprising a low temperature rubber-like copolymer of 97% isobutylene and 3% isoprene together with 0.1 to 2% by weight of the condensation product pre pared by reacting resorcinol and butadiene in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

8. A composition of matter comprising a rubber-like polymer of isobutylene and the condensation product prepared by reacting a diolefin and a polyhydric phenol in the presence of a hydrate of ferric chloride. the said condensation product containing two aromatic nuclei.

9. Product of claim 8 in which the diolefin is butadiene and the polyhydric phenol is resorcinol.

10. Product of claim 8 in which the diolefin is isoprene and the polyhydric phenol is resorcinol.

11. A composition of matter comprising a low temperature rubber-like copolymer of a major proportion of iso'butylene with a minor proportion of a diolefin together with the condensation product prepared by reacting a, diolefin and a polyhydric phenol in the presence of a hydrate of ferric chloride, the said condensation product containing two aromatic nuclei.

12. A product of claim 11 in which the diolefin is butadiene and the polyhydric phenol is resorcinol.

13. A product of claim 11 in which the diolefin is isoprene and the polyhydric phenol is resorcinol.

WILLIAM F. AREY, JR. ROBERT E. WOOD.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Schaad Mar. 13, 1945 Van Gilder May 17, 1949 OTHER REFERENCES Hackhs Chemical Dictionary, 3rd Ed., page 219, June 22, 1944. Blakiston Co., Philadelphia,

Number 

1. A HIGH MOLECULAR WEIGHT ELASTOMERIC POLYMERIZATION PRODUCT OF A FEED CONTAINING AT LEAST A MAJOR PROPORTION OF ALIPHATIC HYDROCARBON COMPOUND SELECTED FROM THE GROUP CONSISTING OF MONO-OLEFINS AND MULTI-OLEFINS HAVING FROM 4 TO 14 CARBONS ATOMS PER MOLECULE AND WHICH IS NORMALLY SUBJECT TO DETERIORATION IN THE PRESENCE OF OXYGEN, WHICH CONTAINS IN ADMIXTURE THEREWITH A SMALL QUANTITY, SUFFICIENT TO SUBSTANTIALLY REDUCE SUCH DETERIORATION, OF THE CONDENSATION PRODUCT PREPARED BY REACTING A DIOLEFIN AND A POLYHYDRIC PHENOL IN THE PRESENCE OF A HYDRATE OF FERRIC CHLORIDE, THE SAID CONDENSATION PRODUCT CONTAINING TWO ARMOATIC NUCLEI. 